Liquid crystal display device

ABSTRACT

A multi-domain vertical alignment liquid crystal display device includes a data line, a first gate line, a second gate line, a first sub-pixel unit, and a second sub-pixel unit. The first sub-pixel unit includes a first switch, a first liquid-crystal capacitor and a first storage capacitor. The first switch functions to control writing the data signal of the data line into the first liquid-crystal and storage capacitors based on the first gate signal of the first gate line. The second sub-pixel unit includes a second switch, a second liquid-crystal capacitor, an auxiliary switch, a second storage capacitor and a third storage capacitor. The second and auxiliary switches are employed to control writing the data signal into the second liquid-crystal capacitor, the second storage capacitor and the third storage capacitor based on the first gate signal and the second gate signal of the second gate line respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to a multi-domain vertical alignment (MVA) liquidcrystal display device.

2. Description of the Prior Art

Because the liquid crystal display (LCD) device has advantages of thinappearance, low power consumption, and low radiation, the LCD device hasbeen widely applied in various electronic products such as computermonitors, mobile phones, personal digital assistants (PDAs), and flatpanel televisions, etc. In general, the LCD device comprises a liquidcrystal layer encapsulated by two substrates. The operation of an LCDdevice is featured by varying voltage drops between opposite sides ofthe liquid crystal layer for twisting the angles of the liquid crystalmolecules in the liquid crystal layer so that the transmittance of theliquid crystal layer can be controlled for illustrating images with theaid of the light source provided by a backlight module.

However, the viewing angle of a conventional LCD device is notsufficiently wide to ensure high display quality, therefore limiting thedevelopment of LCDs. For that reason, a multi-domain vertical alignment(MVA) LCD device is made to increase the viewing angle. A 4-domainvertical alignment LCD device was initially developed for achieving awide viewing angle image display. In the structure of the 4-domainvertical alignment LCD device, each pixel unit has only one sub-pixelunit, which results in a color washout phenomenon occurring to anoblique viewing angle of the 4-domain vertical alignment LCD device. Forthat reason, an 8-domain vertical alignment LCD device is developed forsolving the color washout problem. In the structure of the 8-domainvertical alignment LCD device, each pixel unit includes two sub-pixelunits for achieving a feature of wide viewing angle without anoccurrence of the color washout phenomenon. That is, based on gray levelaveraging effect of two gamma curves corresponding to the two sub-pixelunits, optimal visual experience can be realized in different viewingangles, for achieving a high-quality wide viewing angle image display.

FIG. 1 is a circuit diagram schematically showing a prior MVA liquidcrystal display device. As shown in FIG. 1, the liquid crystal displaydevice 100 comprises a pixel unit 180, a data line Dn, a data line Dn+1,a gate line Gma, a gate line Gmb, and a storage capacitor line (alsotermed as a common line) 190. The pixel unit 180 comprises a firstsub-pixel unit 110 and a second sub-pixel unit 120. The first sub-pixelunit 110 includes a thin film transistor (TFT) 115, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit120 includes a thin film transistor 125, a liquid crystal capacitorClcb, and a storage capacitor Cstb. The thin film transistor 115 iselectrically connected to the data line Dn and the gate line Gma. Thethin film transistor 125 is electrically connected to the data line Dnand the gate line Gmb. Although the LCD device 100 is able to achieve anMVA wide viewing angle image display by controlling the transmittancesof the first sub-pixel unit 110 and the second sub-pixel unit 120through making use of the date signals delivered by the data line Dn,the pixel unit 180 requires two gate lines Gma and Gmb for providing twogate signals so as to control two thin film transistor 115 and 125. Thatis, the number of gate lines required by the LCD device 100 is twice thenumber of gate lines required by a conventional LCD device, andtherefore the aperture ratio of each pixel unit in the LCD device 100 issignificantly reduced. Furthermore, the frequency of driving clock usedin the LCD device 100 is also twice the frequency of driving clock usedin a conventional LCD device. For that reason, compared with aconventional LCD device, the LCD device 100 is rather costly, and theoperation power consumption is increased significantly.

There is another prior-art MVA liquid crystal display device having eachpixel unit electrically connected to just one gate line. However,regarding this prior-art MVA liquid crystal display device, one of twosub-pixel units in each pixel unit has a floating electrode, andtherefore a phenomenon of static charge accumulation is likely to occurduring a long-term operation, which in turn causes an occurrence ofpermanent image sticking effect and the image display quality is thendegraded significantly.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, a liquidcrystal display device capable of achieving an MVA wide viewing angleimage display based on simplified structure is provided. The liquidcrystal display device comprises a data line, a first gate line, asecond gate line, a first sub-pixel unit, and a second sub-pixel unit.The data line is employed to deliver a data signal. The first gate lineis employed to deliver a first gate signal. The second gate line isemployed to deliver a second gate signal. The first sub-pixel unitcomprises a first data switch, a first liquid crystal capacitor, and afirst storage capacitor. The first data switch comprises a first endelectrically connected to the data line for receiving the data signal, agate end electrically connected to the first gate line for receiving thefirst gate signal, and a second end. The first liquid crystal capacitorcomprises a first end electrically connected to the second end of thefirst data switch and a second end for receiving a first common voltage.The first storage capacitor comprises a first end electrically connectedto the second end of the first data switch and a second end forreceiving a second common voltage. The second sub-pixel unit comprises asecond data switch, a second liquid crystal capacitor, an auxiliaryswitch, a second storage capacitor, and a third storage capacitor. Thesecond data switch comprises a first end electrically connected to thedata line for receiving the data signal, a gate end electricallyconnected to the first gate line for receiving the first gate signal,and a second end. The second liquid crystal capacitor comprises a firstend electrically connected to the second end of the second data switchand a second end for receiving the first common voltage. The auxiliaryswitch comprises a first end electrically connected to the second end ofthe second data switch, a gate end electrically connected to the secondgate line for receiving the second gate signal, and a second end. Thesecond storage capacitor comprises a first end electrically connected tothe second end of the auxiliary switch and a second end for receivingthe second common voltage. The third storage capacitor comprises a firstend electrically connected to the second end of the second data switchand a second end electrically connected to the second end of theauxiliary switch.

In accordance with another embodiment of the present invention, a liquidcrystal display device capable of achieving an MVA wide viewing angleimage display based on simplified structure is provided. The liquidcrystal display device comprises a data line, a first gate line, asecond gate line, a first sub-pixel unit, and a second sub-pixel unit.The data line is employed to deliver a data signal. The first gate lineis employed to deliver a first gate signal. The second gate line isemployed to deliver a second gate signal. The first sub-pixel unitcomprises a first data switch, a first liquid crystal capacitor, and afirst storage capacitor. The first data switch comprises a first endelectrically connected to the data line for receiving the data signal, agate end electrically connected to the first gate line for receiving thefirst gate signal, and a second end. The first liquid crystal capacitorcomprises a first end electrically connected to the second end of thefirst data switch and a second end for receiving a first common voltage.The first storage capacitor comprises a first end electrically connectedto the second end of the first data switch and a second end forreceiving a second common voltage. The second sub-pixel unit comprises asecond data switch, a second liquid crystal capacitor, an auxiliaryswitch, a second storage capacitor, a third storage capacitor, and afourth storage capacitor. The second data switch comprises a first endelectrically connected to the data line for receiving the data signal, agate end electrically connected to the first gate line for receiving thefirst gate signal, and a second end. The second liquid crystal capacitorcomprises a first end electrically connected to the second end of thesecond data switch and a second end for receiving the first commonvoltage. The auxiliary switch comprises a first end for receiving thesecond common voltage, a gate end electrically connected to the secondgate line for receiving the second gate signal, and a second end. Thesecond storage capacitor comprises a first end electrically connected tothe second end of the auxiliary switch and a second end for receivingthe second common voltage. The third storage capacitor comprises a firstend electrically connected to the second end of the second data switchand a second end electrically connected to the second end of theauxiliary switch. The fourth storage capacitor comprises a first endelectrically connected to the second end of the second data switch and asecond end for receiving the second common voltage.

In accordance with another embodiment of the present invention, a liquidcrystal display device capable of achieving an MVA wide viewing angleimage display based on simplified structure is provided. The liquidcrystal display device comprises a data line, a first gate line, asecond gate line, a first sub-pixel unit, and a second sub-pixel unit.The data line is employed to deliver a data signal. The first gate lineis employed to deliver a first gate signal. The second gate line isemployed to deliver a second gate signal. The first sub-pixel unitcomprises a first data switch, a first liquid crystal capacitor, and afirst storage capacitor. The first data switch comprises a first endelectrically connected to the data line for receiving the data signal, agate end electrically connected to the first gate line for receiving thefirst gate signal, and a second end. The first liquid crystal capacitorcomprises a first end electrically connected to the second end of thefirst data switch and a second end for receiving a first common voltage.The first storage capacitor comprises a first end electrically connectedto the second end of the first data switch and a second end forreceiving a second common voltage. The second sub-pixel unit comprises asecond data switch, a second liquid crystal capacitor, a second storagecapacitor, an auxiliary switch, and a third storage capacitor. Thesecond data switch comprises a first end electrically connected to thedata line for receiving the data signal, a gate end electricallyconnected to the first gate line for receiving the first gate signal,and a second end. The second liquid crystal capacitor comprises a firstend electrically connected to the second end of the second data switchand a second end for receiving the first common voltage. The secondstorage capacitor comprises a first end electrically connected to thesecond end of the second data switch and a second end for receiving thesecond common voltage. The auxiliary switch comprises a first endelectrically connected to the second end of the second data switch, agate end electrically connected to the second gate line for receivingthe second gate signal, and a second end. The third storage capacitorcomprises a first end electrically connected to the second end of theauxiliary switch and a second end for receiving the second commonvoltage.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram schematically showing a prior MVA liquidcrystal display device.

FIG. 2 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a first embodiment of the presentinvention.

FIG. 3 shows related signal waveforms regarding operations of the LCDdevice in FIG. 2, having time along the abscissa.

FIG. 4 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a second embodiment of the presentinvention.

FIG. 5 shows related signal waveforms regarding operations of the LCDdevice in FIG. 4, having time along the abscissa.

FIG. 6 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a third embodiment of the presentinvention.

FIG. 7 shows related signal waveforms regarding operations of the LCDdevice in FIG. 6, having time along the abscissa.

FIG. 8 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a fourth embodiment of the presentinvention.

FIG. 9 shows related signal waveforms regarding operations of the LCDdevice in FIG. 8, having time along the abscissa.

FIG. 10 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a fifth embodiment of the presentinvention.

FIG. 11 shows related signal waveforms regarding operations of the LCDdevice in FIG. 10, having time along the abscissa.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Here,it is to be noted that the present invention is not limited thereto.

FIG. 2 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a first embodiment of the presentinvention. As shown in FIG. 2, the LCD device 200 comprises a pixel unit280, a data line Dn, a gate line Gm, and a gate line Gm+1. The gate lineGm+1 is adjacent to the gate line Gm. The pixel unit 280 comprises afirst sub-pixel unit 210 and a second sub-pixel unit 220. The firstsub-pixel unit 210 includes a data switch 215, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit220 includes a data switch 225, an auxiliary switch 230, a liquidcrystal capacitor Clcb, a storage capacitor Cstb, and a storagecapacitor Cstc. The data switches 215, 225 and the auxiliary switch 230are thin film transistors or metal oxide semiconductor (MOS) fieldeffect transistors.

The data switch 215 comprises a first end electrically connected to thedata line Dn for receiving a data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving a gate signal SGm, and asecond end for outputting a first voltage Va. The liquid crystalcapacitor Clca comprises a first end electrically connected to thesecond end of the data switch 215 and a second end for receiving a firstcommon voltage Vcom1. The storage capacitor Csta comprises a first endelectrically connected to the second end of the data switch 215 and asecond end for receiving a second common voltage Vcom2. The capacitanceof the liquid crystal capacitor Clca is identical to or different fromthe capacitance of the liquid crystal capacitor Clcb. The capacitancesof the storage capacitors Csta, Cstb and Cstc are identical ordifferent. The second common voltage Vcom2 is identical to or differentfrom the first common voltage Vcom1.

The data switch 225 comprises a first end electrically connected to thedata line Dn for receiving the data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving the gate signal SGm, and asecond end for outputting a second voltage Vb. The liquid crystalcapacitor Clcb comprises a first end electrically connected to thesecond end of the data switch 225 and a second end for receiving thefirst common voltage Vcom1. The auxiliary switch 230 comprises a firstend electrically connected to the second end of the data switch 225, agate end electrically connected to the gate line Gm+1 for receiving agate signal SGm+1, and a second end. The storage capacitor Cstbcomprises a first end electrically connected to the second end of theauxiliary switch 230 and a second end for receiving the second commonvoltage Vcom2. The storage capacitor Cstc comprises a first endelectrically connected to the second end of the data switch 225 and asecond end electrically connected to the second end of the auxiliaryswitch 230.

FIG. 3 shows related signal waveforms regarding operations of the LCDdevice 200 in FIG. 2, having time along the abscissa. The signalwaveforms in FIG. 3, from top to bottom, are the gate signal SGm, thegate signal SGm+1, the data signal SDn, the first voltage Va, and thesecond voltage Vb. The data signal SDn is assumed to retain a voltage Vsin a short time including intervals T1 and T2. As shown in FIG. 3, thegate signal SGm has high voltage level and the gate signal SGm+1 has lowvoltage level during the interval T1, therefore the data switches 215,225 are turned on and the auxiliary switch 230 is turned off.Accordingly, both the first voltage Va and the second voltage Vb becomethe voltage Vs. In the meantime, the second end of the data switch 225stores a charge amount Qb1 of an equivalent capacitor corresponding tothe second sub-pixel unit 220. The charge amount Qb1 can be expressed asFormula (1) listed below.

$\begin{matrix}{{{Qb}\; 1} = {\lbrack {{Clcbv} + \frac{Cstbv}{1 + \frac{Cstbv}{Cstcv}}} \rbrack{Vs}}} & {{Formula}\mspace{14mu}(1)}\end{matrix}$

In Formula (1), Clcbv, Cstbv, and Cstcv represent the capacitances ofthe liquid crystal capacitor Clcb and the storage capacitors Cstb, Cstcrespectively. During the interval T2, the gate signal SGm is switchingto low voltage level and the gate signal SGm+1 is switching to highvoltage level, therefore the data switches 215, 225 are turned off andthe auxiliary switch 230 is turned on. For that reason, the firstvoltage Va holds the voltage Vs; however, the second voltage Vb isswitching to become a voltage Vsx following an occurrence ofshort-circuit between the first and second ends of the storage capacitorCstc caused by turning on the auxiliary switch 230. The voltage Vsx canbe deduced based on a conservation rule of the charge amount Qb1 and isexpressed as Formula (2) listed below.

$\begin{matrix}{{Vsx} = {{\frac{\lbrack {{Clcbv} + \frac{Cstbv}{1 + \frac{Cstbv}{Cstcv}}} \rbrack}{( {{Clcbv} + {Cstbv}} )}{Vs}} = {\alpha\;{Vs}}}} & {{Formula}\mspace{14mu}(2)}\end{matrix}$

In Formula (2), a is a predetermined proportional constant. After theinterval T2, the first sub-pixel unit 210 and the second sub-pixel unit220 are operative to achieve an MVA wide viewing angle image displaybased on the first voltage Va and the second voltage Vb having apredetermined proportional relationship. If the electrode areas of thecapacitors in the pixel unit 280 are well adjusted, the image quality ofthe LCD device 200 can be optimized In summary, since the LCD device 200of the present invention provides different sub-pixel voltages by makinguse of conventional driving feature corresponding to gate signals of twoadjacent gate lines, the number of gate lines required by the LCD device200 is substantially the same as the number of gate lines required by aconventional LCD device. Therefore, the aperture ratio of each pixelunit in the LCD device 200 is not reduced and the frequency of drivingclock used in the LCD device 200 is the same as the frequency of drivingclock used in the conventional LCD device. That is, the LCD device 200is capable of achieving an MVA wide viewing angle image display based ona cost-effective simplified structure. In one embodiment, the LCD device200 is employed to realize high image display quality having wideviewing angle based on 8-domain vertical alignment design. Besides, theLCD device 200 has no floating electrode and is able to maintain highimage display quality during a long-term operation.

FIG. 4 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a second embodiment of the presentinvention. As shown in FIG. 4, the LCD device 400 comprises a pixel unit480, a data line Dn, a gate line Gm, and a gate line Gm+1. The gate lineGm+1 is adjacent to the gate line Gm. The pixel unit 480 comprises afirst sub-pixel unit 410 and a second sub-pixel unit 420. The firstsub-pixel unit 410 includes a data switch 415, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit420 includes a data switch 425, an auxiliary switch 430, a liquidcrystal capacitor Clcb, a storage capacitor Cstb, a storage capacitorCstc, and a storage capacitor Cstd. The data switches 415, 425 and theauxiliary switch 430 are thin film transistors or MOS field effecttransistors.

The data switch 415 comprises a first end electrically connected to thedata line Dn for receiving a data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving a gate signal SGm, and asecond end for outputting a first voltage Va. The liquid crystalcapacitor Clca comprises a first end electrically connected to thesecond end of the data switch 415 and a second end for receiving a firstcommon voltage Vcom1. The storage capacitor Csta comprises a first endelectrically connected to the second end of the data switch 415 and asecond end for receiving a second common voltage Vcom2. The capacitanceof the liquid crystal capacitor Clca is identical to or different fromthe capacitance of the liquid crystal capacitor Clcb. The capacitancesof the storage capacitors Csta, Cstb, Cstc and Cstd are identical ordifferent. The second common voltage Vcom2 is identical to or differentfrom the first common voltage Vcom1.

The data switch 425 comprises a first end electrically connected to thedata line Dn for receiving the data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving the gate signal SGm, and asecond end for outputting a second voltage Vb. The liquid crystalcapacitor Clcb comprises a first end electrically connected to thesecond end of the data switch 425 and a second end for receiving thefirst common voltage Vcom1. The auxiliary switch 430 comprises a firstend electrically connected to the second end of the data switch 425, agate end electrically connected to the gate line Gm+1 for receiving agate signal SGm+1, and a second end. The storage capacitor Cstbcomprises a first end electrically connected to the second end of theauxiliary switch 430 and a second end for receiving the second commonvoltage Vcom2. The storage capacitor Cstc comprises a first endelectrically connected to the second end of the data switch 425 and asecond end electrically connected to the second end of the auxiliaryswitch 430. The storage capacitor Cstd comprises a first endelectrically connected to the second end of the data switch 425 and asecond end for receiving the second common voltage Vcom2.

FIG. 5 shows related signal waveforms regarding operations of the LCDdevice 400 in FIG. 4, having time along the abscissa. The signalwaveforms in FIG. 5, from top to bottom, are the gate signal SGm, thegate signal SGm+1, the data signal SDn, the first voltage Va, and thesecond voltage Vb. The data signal SDn is assumed to retain a voltage Vsin a short time including intervals T1 and T2. As shown in FIG. 5, thegate signal SGm has high voltage level and the gate signal SGm+1 has lowvoltage level during the interval T1, therefore the data switches 415,425 are turned on and the auxiliary switch 430 is turned off.Accordingly, both the first voltage Va and the second voltage Vb becomethe voltage Vs. In the meantime, the second end of the data switch 425stores a charge amount Qb2 of an equivalent capacitor corresponding tothe second sub-pixel unit 420. The charge amount Qb2 can be expressed asFormula (3) listed below.

$\begin{matrix}{{{Qb}\; 2} = {\lbrack {{Clcbv} + \frac{Cstbv}{1 + \frac{Cstbv}{Cstcv}} + {Cstdv}} \rbrack{Vs}}} & {{Formula}\mspace{14mu}(3)}\end{matrix}$

In Formula (3), Clcbv, Cstbv, Cstcv, and Cstdv represent thecapacitances of the liquid crystal capacitor Clcb and the storagecapacitors Cstb, Cstc, Cstd respectively. During the interval T2, thegate signal SGm is switching to low voltage level and the gate signalSGm+1 is switching to high voltage level, therefore the data switches415, 425 are turned off and the auxiliary switch 430 is turned on. Forthat reason, the first voltage Va holds the voltage Vs; however, thesecond voltage Vb is switching to become a voltage Vsy following anoccurrence of short-circuit between the first and second ends of thestorage capacitor Cstc caused by turning on the auxiliary switch 430.The voltage Vsy can be deduced based on a conservation rule of thecharge amount Qb2 and is expressed as Formula (4) listed below.

$\begin{matrix}{{Vsy} = {{\frac{\lbrack {{Clcbv} + \frac{Cstbv}{1 + \frac{Cstbv}{Cstcv}} + {Cstdv}} \rbrack}{( {{Clcbv} + {Cstbv} + {Cstdv}} )}{Vs}} = {\beta\;{Vs}}}} & {{Formula}\mspace{14mu}(4)}\end{matrix}$

In Formula (4), β is a predetermined proportional constant. After theinterval T2, the first sub-pixel unit 410 and the second sub-pixel unit420 are operative to achieve an MVA wide viewing angle image displaybased on the first voltage Va and the second voltage Vb having apredetermined proportional relationship. If the electrode areas of thecapacitors in the pixel unit 480 are well adjusted, the image quality ofthe LCD device 400 can be optimized In summary, since the LCD device 400of the present invention provides different sub-pixel voltages by makinguse of conventional driving feature corresponding to gate signals of twoadjacent gate lines, the number of gate lines required by the LCD device400 is substantially the same as the number of gate lines required by aconventional LCD device. Therefore, the aperture ratio of each pixelunit in the LCD device 400 is not reduced and the frequency of drivingclock used in the LCD device 400 is the same as the frequency of drivingclock used in the conventional LCD device. That is, the LCD device 400is capable of achieving an MVA wide viewing angle image display based ona cost-effective simplified structure. In one embodiment, the LCD device400 is employed to realize high image display quality having wideviewing angle based on 8-domain vertical alignment design. Besides, theLCD device 400 has no floating electrode and is able to maintain highimage display quality during a long-term operation.

FIG. 6 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a third embodiment of the presentinvention. As shown in FIG. 6, the LCD device 600 comprises a pixel unit680, a data line Dn, a gate line Gm, and a gate line Gm+1. The gate lineGm+1 is adjacent to the gate line Gm. The pixel unit 680 comprises afirst sub-pixel unit 610 and a second sub-pixel unit 620. The firstsub-pixel unit 610 includes a data switch 615, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit620 includes a data switch 625, an auxiliary switch 630, a liquidcrystal capacitor Clcb, a storage capacitor Cstb, a storage capacitorCstc, and a storage capacitor Cstd. The data switches 615, 625 and theauxiliary switch 630 are thin film transistors or MOS field effecttransistors.

The data switch 615 comprises a first end electrically connected to thedata line Dn for receiving a data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving a gate signal SGm, and asecond end for outputting a first voltage Va. The liquid crystalcapacitor Clca comprises a first end electrically connected to thesecond end of the data switch 615 and a second end for receiving a firstcommon voltage Vcom1. The storage capacitor Csta comprises a first endelectrically connected to the second end of the data switch 615 and asecond end for receiving a second common voltage Vcom2. The capacitanceof the liquid crystal capacitor Clca is identical to or different fromthe capacitance of the liquid crystal capacitor Clcb. The capacitancesof the storage capacitors Csta, Cstb, Cstc and Cstd are identical ordifferent. The second common voltage Vcom2 is identical to or differentfrom the first common voltage Vcom1.

The data switch 625 comprises a first end electrically connected to thedata line Dn for receiving the data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving the gate signal SGm, and asecond end for outputting a second voltage Vb. The liquid crystalcapacitor Clcb comprises a first end electrically connected to thesecond end of the data switch 625 and a second end for receiving thefirst common voltage Vcom1. The auxiliary switch 630 comprises a firstend for receiving the second common voltage Vcom2, a gate endelectrically connected to the gate line Gm+1 for receiving a gate signalSGm+1, and a second end. The storage capacitor Cstb comprises a firstend electrically connected to the second end of the auxiliary switch 630and a second end for receiving the second common voltage Vcom2. Thestorage capacitor Cstc comprises a first end electrically connected tothe second end of the data switch 625 and a second end electricallyconnected to the second end of the auxiliary switch 630. The storagecapacitor Cstd comprises a first end electrically connected to thesecond end of the data switch 625 and a second end for receiving thesecond common voltage Vcom2.

FIG. 7 shows related signal waveforms regarding operations of the LCDdevice 600 in FIG. 6, having time along the abscissa. The signalwaveforms in FIG. 7, from top to bottom, are the gate signal SGm, thegate signal SGm+1, the data signal SDn, the first voltage Va, and thesecond voltage Vb. The data signal SDn is assumed to retain a voltage Vsin a short time including intervals T1 and T2. As shown in FIG. 7, thegate signal SGm has high voltage level and the gate signal SGm+1 has lowvoltage level during the interval T1, therefore the data switches 615,625 are turned on and the auxiliary switch 630 is turned off.Accordingly, both the first voltage Va and the second voltage Vb becomethe voltage Vs. In the meantime, the equivalent capacitor of the secondsub-pixel unit 620 stores a charge amount Qb3 at the second end of thedata switch 625. The charge amount Qb3 can be expressed as Formula (5)listed below.

$\begin{matrix}{{{Qb}\; 3} = {\lbrack {{Clcbv} + \frac{Cstcv}{1 + \frac{Cstcv}{Cstbv}} + {Cstdv}} \rbrack{Vs}}} & {{Formula}\mspace{14mu}(5)}\end{matrix}$

In Formula (5), Clcbv, Cstbv, Cstcv, and Cstdv represent thecapacitances of the liquid crystal capacitor Clcb and the storagecapacitors Cstb, Cstc, Cstd respectively. During the interval T2, thegate signal SGm is switching to low voltage level and the gate signalSGm+1 is switching to high voltage level, therefore the data switches615, 625 are turned off and the auxiliary switch 630 is turned on. Forthat reason, the first voltage Va holds the voltage Vs; however, thesecond voltage Vb is switching to become a voltage Vsp following anoccurrence of short-circuit between the first and second ends of thestorage capacitor Cstb caused by turning on the auxiliary switch 630.The voltage Vsp can be deduced based on a conservation rule of thecharge amount Qb3 and is expressed as Formula (6) listed below.

$\begin{matrix}{{Vsp} = {{\frac{\lbrack {{Clcbv} + \frac{Cstcv}{1 + \frac{Cstcv}{Cstbv}} + {Cstdv}} \rbrack}{( {{Clcbv} + {Cstcv} + {Cstdv}} )}{Vs}} = {\gamma\;{Vs}}}} & {{Formula}\mspace{14mu}(6)}\end{matrix}$

In Formula (6), γ is a predetermined proportional constant. After theinterval T2, the first sub-pixel unit 610 and the second sub-pixel unit620 are operative to achieve an MVA wide viewing angle image displaybased on the first voltage Va and the second voltage Vb having apredetermined proportional relationship. If the electrode areas of thecapacitors in the pixel unit 680 are well adjusted, the image quality ofthe LCD device 600 can be optimized In summary, since the LCD device 600of the present invention provides different sub-pixel voltages by makinguse of conventional driving feature corresponding to gate signals of twoadjacent gate lines, the number of gate lines required by the LCD device600 is substantially the same as the number of gate lines required by aconventional LCD device. Therefore, the aperture ratio of each pixelunit in the LCD device 600 is not reduced and the frequency of drivingclock used in the LCD device 600 is the same as the frequency of drivingclock used in the conventional LCD device. That is, the LCD device 600is capable of achieving an MVA wide viewing angle image display based ona cost-effective simplified structure. In one embodiment, the LCD device600 is employed to realize high image display quality having wideviewing angle based on 8-domain vertical alignment design. Besides, theLCD device 600 has no floating electrode and is able to maintain highimage display quality during a long-term operation.

FIG. 8 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a fourth embodiment of the presentinvention. As shown in FIG. 8, the LCD device 700 comprises a pixel unit780, a data line Dn, a gate line Gm, and a gate line Gm+1. The gate lineGm+1 is adjacent to the gate line Gm. The pixel unit 780 comprises afirst sub-pixel unit 710 and a second sub-pixel unit 720. The firstsub-pixel unit 710 includes a data switch 715, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit720 includes a data switch 725, an auxiliary switch 730, a liquidcrystal capacitor Clcb, a storage capacitor Cstb, and a storagecapacitor Cstc. The data switches 715, 725 and the auxiliary switch 730are thin film transistors or MOS field effect transistors.

The data switch 715 comprises a first end electrically connected to thedata line Dn for receiving a data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving a gate signal SGm, and asecond end for outputting a first voltage Va. The liquid crystalcapacitor Clca comprises a first end electrically connected to thesecond end of the data switch 715 and a second end for receiving a firstcommon voltage Vcom1. The storage capacitor Csta comprises a first endelectrically connected to the second end of the data switch 715 and asecond end for receiving a second common voltage Vcom2. The capacitanceof the liquid crystal capacitor Clca is identical to or different fromthe capacitance of the liquid crystal capacitor Clcb. The capacitancesof the storage capacitors Csta, Cstb and Cstc are identical ordifferent. The second common voltage Vcom2 is identical to or differentfrom the first common voltage Vcom1.

The data switch 725 comprises a first end electrically connected to thedata line Dn for receiving the data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving the gate signal SGm, and asecond end for outputting a second voltage Vb. The liquid crystalcapacitor Clcb comprises a first end electrically connected to thesecond end of the data switch 725 and a second end for receiving thefirst common voltage Vcom1. The storage capacitor Cstb comprises a firstend electrically connected to the second end of the data switch 725 anda second end for receiving the second common voltage Vcom2. Theauxiliary switch 730 comprises a first end electrically connected to thesecond end of the data switch 725, a gate end electrically connected tothe gate line Gm+1 for receiving a gate signal SGm+1, and a second end.The storage capacitor Cstc comprises a first end electrically connectedto the second end of the auxiliary switch 730 and a second end forreceiving the second common voltage Vcom2.

FIG. 9 shows related signal waveforms regarding operations of the LCDdevice 700 in FIG. 8, having time along the abscissa. The signalwaveforms in FIG. 9, from top to bottom, are the gate signal SGm, thegate signal SGm+1, the data signal SDn, the first voltage Va, and thesecond voltage Vb. The data signal SDn is assumed to hold a voltage Vsor −Vs in a short time including an Ith frame time, a (I+1)th frame timethrough a Jth frame time. For instance, the data signal SDn holds avoltage Vs during the Ith frame time; the data signal SDn holds avoltage −Vs during the (I+1) th frame time; and the data signal SDnholds a voltage Vs during the Jth frame time. As shown in FIG. 9, thegate signal SGm has high voltage level and the gate signal SGm+1 has lowvoltage level during an interval Ti1 of the Ith frame time, thereforethe data switches 715, 725 are turned on and the auxiliary switch 730 isturned off. Accordingly, both the first voltage Va and the secondvoltage Vb become the voltage Vs. In the meantime, the second end of thedata switch 725 stores a charge amount Qb4 of an equivalent capacitorcorresponding to the liquid crystal capacitor Clcb and the storagecapacitor Cstb connected in parallel. The charge amount Qb4 can beexpressed as Formula (7) listed below.Qb4=[Clcbv+Cstb]Vs  Formula (7)

In Formula (7), Clcbv and Cstbv represent the capacitances of the liquidcrystal capacitor Clcb and the storage capacitors Cstb respectively.During an interval Ti2 of the Ith frame time, the gate signal SGm isswitching to low voltage level and the gate signal SGm+1 is switching tohigh voltage level, therefore the data switches 715, 725 are turned offand the auxiliary switch 730 is turned on. For that reason, the firstvoltage Va holds the voltage Vs; however, the second voltage Vb isswitching to become a voltage Vszi because of turning on the auxiliaryswitch 730. The voltage Vszi can be deduced based on a conservation ruleof the charge amount Qb4 and is expressed as Formula (8) listed below.

$\begin{matrix}{{Vszi} = {\frac{( {{Clcbv} + {Cstbv}} )}{( {{Clcbv} + {Cstbv} + {Cstcv}} )}{Vs}}} & {{Formula}\mspace{14mu}(8)}\end{matrix}$

In Formula (8), Cstcv represents the capacitance of the storagecapacitors Cstc. At this time, the first end of the storage capacitorsCstc stores a charge amount Qc1. The charge amount Qc1 can be expressedas Formula (9) listed below.

$\begin{matrix}{{{Qc}\; 1} = {{{Vszi} \times {Cstcv}} = {\frac{( {{Clcbv} + {Cstbv}} ){Cstcv}}{( {{Clcbv} + {Cstbv} + {Cstcv}} )}{Vs}}}} & {{Formula}\mspace{14mu}(9)}\end{matrix}$

During an interval T(i+1)1 of the (I+1)th frame time, the gate signalSGm has high voltage level and the gate signal SGm+1 has low voltagelevel, therefore the data switches 715, 725 are turned on and theauxiliary switch 730 is turned off. Accordingly, both the first voltageVa and the second voltage Vb become the voltage −Vs. In the meantime,the second end of the data switch 725 stores a charge amount −Qb4 of theequivalent capacitor corresponding to the liquid crystal capacitor Clcband the storage capacitor Cstb connected in parallel.

During an interval T(i+1)2 of the (I+1)th frame time, the gate signalSGm is switching to low voltage level and the gate signal SGm+1 isswitching to high voltage level, therefore the data switches 715, 725are turned off and the auxiliary switch 730 is turned on. For thatreason, the first voltage Va holds the voltage −Vs; however, the secondvoltage Vb is switching to become a voltage −Vsz(i+1) because of turningon the auxiliary switch 730. The voltage Vsz(i+1) can be deduced basedon a conservation rule of the charge amount (Qb4−Qc1) and is expressedas Formula (10) listed below.

$\begin{matrix}{{{Vsz}( {i + 1} )} = {{\frac{( {{Clcbv} + {Cstbv}} )}{( {{Clcbv} + {Cstbv} + {Cstcv}} )}\lbrack {1 - \frac{Cstcv}{{Clcbv} + {Cstbv} + {Cstcv}}} \rbrack}{Vs}}} & {{Formula}\mspace{14mu}(10)}\end{matrix}$

When the second voltage Vb reaches steady state at the Jth frame timeafter several frame times subsequent to the (I+1) th frame time, thesecond voltage Vb becomes a voltage Vszj. Based on the aforementionedFormula (7) through Formula (10), the voltage Vszj can be deduced and isexpressed as Formula (11) listed below.

$\begin{matrix}\begin{matrix}{{Vszj} = \frac{{Clcbv} + {Cstbv}}{{Clcbv} + {Cstbv} + {Cstcv}}} \\{\lbrack {1 - \frac{Cstcv}{{Clcbv} + {Cstbv} + {Cstcv}} +} } \\{ {( \frac{Cstcv}{{Clcbv} + {Cstbv} + {Cstcv}} )^{2} - \ldots} \rbrack{Vs}} \\{= {\frac{( {{Clcbv} + {Cstbv}} )}{( {{Clcbv} + {Cstbv} + {2{Cstcv}}} )}{Vs}}} \\{= {\lambda\;{Vs}}}\end{matrix} & {{Formula}\mspace{14mu}(11)}\end{matrix}$

In Formula (11), λ is a predetermined proportional constant. After theinterval Tj2, the first sub-pixel unit 710 and the second sub-pixel unit720 are operative to achieve an MVA wide viewing angle image displaybased on the first voltage Va and the second voltage Vb having apredetermined proportional relationship. In the operation of the LCDdevice 700, the second voltage Vb may be sort of unstable under highframe variation rate. However, under general operation situation, anoccurrence of serious image flickering phenomena can be avoided and theLCD device 700 is still able to maintain high display quality.

In summary, since the LCD device 700 of the present invention providesdifferent sub-pixel voltages by making use of conventional drivingfeature corresponding to gate signals of two adjacent gate lines, thenumber of gate lines required by the LCD device 700 is substantially thesame as the number of gate lines required by a conventional LCD device.Therefore, the aperture ratio of each pixel unit in the LCD device 700is not reduced and the frequency of driving clock used in the LCD device700 is the same as the frequency of driving clock used in theconventional LCD device. That is, the LCD device 700 is capable ofachieving an MVA wide viewing angle image display based on acost-effective simplified structure. In one embodiment, the LCD device700 is employed to realize high image display quality having wideviewing angle based on 8-domain vertical alignment design. Besides, theLCD device 700 has no floating electrode and is able to maintain highimage display quality during a long-term operation.

FIG. 10 is a circuit diagram schematically showing an MVA liquid crystaldisplay device in accordance with a fifth embodiment of the presentinvention. As shown in FIG. 10, the LCD device 900 comprises a pixelunit 980, a data line Dn, a gate line Gm, and a gate line Gm+1. The gateline Gm+1 is adjacent to the gate line Gm. The pixel unit 980 comprisesa first sub-pixel unit 910 and a second sub-pixel unit 920. The firstsub-pixel unit 910 includes a data switch 915, a liquid crystalcapacitor Clca, and a storage capacitor Csta. The second sub-pixel unit920 includes a data switch 925, an auxiliary switch 930, an auxiliaryswitch 935, a liquid crystal capacitor Clcb, a storage capacitor Cstb,and a storage capacitor Cstc. The data switches 915, 925 and theauxiliary switches 930, 935 are thin film transistors or MOS fieldeffect transistors.

The data switch 915 comprises a first end electrically connected to thedata line Dn for receiving a data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving a gate signal SGm, and asecond end for outputting a first voltage Va. The liquid crystalcapacitor Clca comprises a first end electrically connected to thesecond end of the data switch 915 and a second end for receiving a firstcommon voltage Vcom1. The storage capacitor Csta comprises a first endelectrically connected to the second end of the data switch 915 and asecond end for receiving a second common voltage Vcom2. The capacitanceof the liquid crystal capacitor Clca is identical to or different fromthe capacitance of the liquid crystal capacitor Clcb. The capacitancesof the storage capacitors Csta, Cstb and Cstc are identical ordifferent. The second common voltage Vcom2 is identical to or differentfrom the first common voltage Vcom1.

The data switch 925 comprises a first end electrically connected to thedata line Dn for receiving the data signal SDn, a gate end electricallyconnected to the gate line Gm for receiving the gate signal SGm, and asecond end for outputting a second voltage Vb. The liquid crystalcapacitor Clcb comprises a first end electrically connected to thesecond end of the data switch 925 and a second end for receiving thefirst common voltage Vcom1. The storage capacitor Cstb comprises a firstend electrically connected to the second end of the data switch 925 anda second end for receiving the second common voltage Vcom2. Theauxiliary switch 930 comprises a first end electrically connected to thesecond end of the data switch 925, a gate end electrically connected tothe gate line Gm+1 for receiving a gate signal SGm+1, and a second end.The storage capacitor Cstc comprises a first end electrically connectedto the second end of the auxiliary switch 930 and a second end forreceiving the second common voltage Vcom2. The auxiliary switch 935comprises a first end electrically connected to the first end of thestorage capacitor Cstc, a gate end electrically connected to the gateline Gm for receiving the gate signal SGm, and a second end forreceiving the second common voltage Vcom2.

FIG. 11 shows related signal waveforms regarding operations of the LCDdevice 900 in FIG. 10, having time along the abscissa. The signalwaveforms in FIG. 11, from top to bottom, are the gate signal SGm, thegate signal SGm+1, the data signal SDn, the first voltage Va, and thesecond voltage Vb. The data signal SDn is assumed to retain a voltage Vsin a short time including intervals T1 and T2. As shown in FIG. 11, thegate signal SGm has high voltage level and the gate signal SGm+1 has lowvoltage level during the interval T1, therefore the data switches 915,925 and the auxiliary switch 935 are turned on and the auxiliary switch930 is turned off. Accordingly, both the first voltage Va and the secondvoltage Vb become the voltage Vs, and the electric charges accumulatedin the storage capacitor Cstc can be released via the auxiliary switch935. In the meantime, the second end of the data switch 925 stores acharge amount Qb5 of the equivalent capacitor corresponding to theliquid crystal capacitor Clcb and the storage capacitor Cstb connectedin parallel. The charge amount Qb5 can be expressed as Formula (12)listed below.Qb5=[Clcbv+Cstbv]Vs  Formula (12)

In Formula (12), Clcbv and Cstbv represent the capacitances of theliquid crystal capacitor Clcb and the storage capacitor Cstbrespectively. During the interval T2, the gate signal SGm is switchingto low voltage level and the gate signal SGm+1 is switching to highvoltage level, therefore the data switches 915, 925 and the auxiliaryswitch 935 are turned off and the auxiliary switch 930 is turned on. Forthat reason, the first voltage Va holds the voltage Vs; however, thesecond voltage Vb is switching to become a voltage Vsw because ofturning on the auxiliary switch 930. The voltage Vsw can be deducedbased on a conservation rule of the charge amount Qb5 and is expressedas Formula (13) listed below.

$\begin{matrix}{{Vsw} = {{\frac{( {{Clcbv} + {Cstbv}} )}{( {{Clcbv} + {Cstbv} + {Cstcv}} )}{Vs}} = {\sigma\;{Vs}}}} & {{Formula}\mspace{14mu}(13)}\end{matrix}$

In Formula (13), Cstcv represent the capacitance of the storagecapacitor Cstc and σ is a predetermined proportional constant. After theinterval T2, the first sub-pixel unit 910 and the second sub-pixel unit920 are operative to achieve an MVA wide viewing angle image displaybased on the first voltage Va and the second voltage Vb having apredetermined proportional relationship. If the electrode areas of thecapacitors in the pixel unit 980 are well adjusted, the image quality ofthe LCD device 900 can be optimized In summary, since the LCD device 900of the present invention provides different sub-pixel voltages by makinguse of conventional driving feature corresponding to gate signals of twoadjacent gate lines, the number of gate lines required by the LCD device900 is substantially the same as the number of gate lines required by aconventional LCD device. Therefore, the aperture ratio of each pixelunit in the LCD device 900 is not reduced and the frequency of drivingclock used in the LCD device 900 is the same as the frequency of drivingclock used in the conventional LCD device. That is, the LCD device 900is capable of achieving an MVA wide viewing angle image display based ona cost-effective simplified structure. In one embodiment, the LCD device900 is employed to realize high image display quality having wideviewing angle based on 8-domain vertical alignment design. Besides, theLCD device 900 has no floating electrode and is able to maintain highimage display quality during a long-term operation.

The present invention is by no means limited to the embodiments asdescribed above by referring to the accompanying drawings, which may bemodified and altered in a variety of different ways without departingfrom the scope of the present invention. Thus, it should be understoodby those skilled in the art that various modifications, combinations,sub-combinations and alternations might occur depending on designrequirements and other factors insofar as they are within the scope ofthe appended claims or the equivalents thereof.

1. A liquid crystal display device comprising: a data line fordelivering a data signal; a first gate line for delivering a first gatesignal; a second gate line for delivering a second gate signal; a firstsub-pixel unit comprising: a first data switch comprising: a first endelectrically connected to the data line for receiving the data signal; agate end electrically connected to the first gate line for receiving thefirst gate signal; and a second end; a first liquid crystal capacitorcomprising: a first end electrically connected to the second end of thefirst data switch; and a second end for receiving a first commonvoltage; and a first storage capacitor comprising: a first endelectrically connected to the second end of the first data switch; and asecond end for receiving a second common voltage; and a second sub-pixelunit comprising: a second data switch comprising: a first endelectrically connected to the data line for receiving the data signal; agate end electrically connected to the first gate line for receiving thefirst gate signal; and a second end; a second liquid crystal capacitorcomprising: a first end electrically connected to the second end of thesecond data switch; and a second end for receiving the first commonvoltage; an auxiliary switch comprising: a first end electricallyconnected to the second end of the second data switch; a gate endelectrically connected to the second gate line for receiving the secondgate signal; and a second end; a second storage capacitor comprising: afirst end directly connected to the second end of the auxiliary switch;and a second end for receiving the second common voltage; and a thirdstorage capacitor comprising: a first end electrically connected to thesecond end of the second data switch; and a second end electricallyconnected to the second end of the auxiliary switch.
 2. The liquidcrystal display device of claim 1, wherein the second gate line isadjacent to the first gate line.
 3. The liquid crystal display device ofclaim 1, wherein the first data switch and the second data switch arethin film transistors or metal oxide semiconductor (MOS) field effecttransistors.
 4. The liquid crystal display device of claim 1, whereinthe auxiliary switch is a thin film transistor or a MOS field effecttransistor.
 5. The liquid crystal display device of claim 1, wherein thefirst sub-pixel unit and the second sub-pixel unit belong to a pixelunit.
 6. The liquid crystal display device of claim 1, wherein thesecond sub-pixel unit further comprises: a fourth storage capacitorcomprising: a first end electrically connected to the second end of thesecond data switch; and a second end for receiving the second commonvoltage.
 7. The liquid crystal display device of claim 1, wherein secondcommon voltage is identical to or different from the first commonvoltage.
 8. A liquid crystal display device comprising: a data line fordelivering a data signal; a first gate line for delivering a first gatesignal; a second gate line for delivering a second gate signal; a firstsub-pixel unit comprising: a first data switch comprising: a first endelectrically connected to the data line for receiving the data signal; agate end electrically connected to the first gate line for receiving thefirst gate signal; and a second end; a first liquid crystal capacitorcomprising: a first end electrically connected to the second end of thefirst data switch; and a second end for receiving a first commonvoltage; and a first storage capacitor comprising: a first endelectrically connected to the second end of the first data switch; and asecond end for receiving a second common voltage; and a second sub-pixelunit comprising: a second data switch comprising: a first endelectrically connected to the data line for receiving the data signal; agate end electrically connected to the first gate line for receiving thefirst gate signal; and a second end; a second liquid crystal capacitorcomprising: a first end electrically connected to the second end of thesecond data switch; and a second end for receiving the first commonvoltage; an auxiliary switch comprising: a first end for receiving thesecond common voltage; a gate end electrically connected to the secondgate line for receiving the second gate signal; and a second end; asecond storage capacitor comprising: a first end directly connected tothe second end of the auxiliary switch; and a second end for receivingthe second common voltage; a third storage capacitor comprising: a firstend directly connected to the second end of the second data switch; anda second end electrically connected to the second end of the auxiliaryswitch; and a fourth storage capacitor comprising: a first end directlyconnected to the second end of the second data switch; and a second endfor receiving the second common voltage.
 9. The liquid crystal displaydevice of claim 8, wherein the second gate line is adjacent to the firstgate line.
 10. The liquid crystal display device of claim 8, wherein thefirst data switch and the second data switch are thin film transistorsor MOS field effect transistors.
 11. The liquid crystal display deviceof claim 8, wherein the auxiliary switch is a thin film transistor or aMOS field effect transistor.
 12. The liquid crystal display device ofclaim 8, wherein second common voltage is identical to or different fromthe first common voltage.
 13. The liquid crystal display device of claim8, wherein the first sub-pixel unit and the second sub-pixel unit belongto a pixel unit.